Re: [TCML] Homemade Crookes Tube?

[w5als via Tesla <tesla@xxxxxxxxxx>]

HI Everyone
   Let me try to put this to rest, crookes tube produce cathode Rays, 
and unless they reflect of
of metal like the railway tube or Maltese cross tube they produce very 
little soft X Rays
at all. I have a large collection of Crookes and geissler tube and have 
check them for X Rays
many time and unless they bounce off metal you have nothing to worry 
about. Even at
10000 volt the railway and Maltese cross tube will produce soft X rays 
but not enough
to hurt you. This is my Flickr site and you can see picture of some of 
them and a video
of them.
https://www.flickr.com/photos/91001059@N08/
the tube in question will not produce harmful X rays.
The information below may help too.
Alton
W5ALS

A *Crookes tube* is an early experimental electrical discharge tube 
<http://en.wikipedia.org/wiki/Discharge_tube>, with partial vacuum, 
invented by English physicist William Crookes 
<http://en.wikipedia.org/wiki/William_Crookes>^[1] 
<http://en.wikipedia.org/wiki/Crookes_tube#cite_note-1> and others 
around 1869-1875,^[2] 
<http://en.wikipedia.org/wiki/Crookes_tube#cite_note-2> in which cathode 
rays <http://en.wikipedia.org/wiki/Cathode_ray>, streams of electrons 
<http://en.wikipedia.org/wiki/Electron>, were discovered.^[3] 
<http://en.wikipedia.org/wiki/Crookes_tube#cite_note-3>
Developed from the earlier Geissler tube 
<http://en.wikipedia.org/wiki/Geissler_tube>, the Crookes tube consists 
of a partially evacuated <http://en.wikipedia.org/wiki/Vacuum> glass 
container of various shapes, with two metal electrodes 
<http://en.wikipedia.org/wiki/Electrodes>, the cathode 
<http://en.wikipedia.org/wiki/Cathode> and the anode 
<http://en.wikipedia.org/wiki/Anode>, one at either end. When a high 
voltage <http://en.wikipedia.org/wiki/High_voltage> is applied between 
the electrodes, cathode rays <http://en.wikipedia.org/wiki/Cathode_ray> 
(electrons <http://en.wikipedia.org/wiki/Electron>) are projected in 
straight lines from the cathode. It was used by Crookes, Johann Hittorf 
<http://en.wikipedia.org/wiki/Johann_Hittorf>, Julius Plücker 
<http://en.wikipedia.org/wiki/Julius_Pl%C3%BCcker>, Eugen Goldstein 
<http://en.wikipedia.org/wiki/Eugen_Goldstein>, Heinrich Hertz 
<http://en.wikipedia.org/wiki/Heinrich_Hertz>, Philipp Lenard 
<http://en.wikipedia.org/wiki/Philipp_Lenard> and others to discover the 
properties of cathode rays, culminating in J.J. Thomson 
<http://en.wikipedia.org/wiki/J.J._Thomson>'s 1897 identification of 
cathode rays as negatively charged particles, which were later named 
/electrons <http://en.wikipedia.org/wiki/Electron>/. Crookes tubes are 
now used only for demonstrating cathode rays.
Wilhelm Röntgen <http://en.wikipedia.org/wiki/Wilhelm_R%C3%B6ntgen> 
discovered X-rays <http://en.wikipedia.org/wiki/X-ray> using the Crookes 
tube in 1895. The term is also used for the first generation, cold 
cathode <http://en.wikipedia.org/wiki/Cold_cathode> X-ray tubes 
<http://en.wikipedia.org/wiki/X-ray_tube>,^[4] 
<http://en.wikipedia.org/wiki/Crookes_tube#cite_note-4> which evolved 
from the experimental Crookes tubes and were used until about 1920.

   How a Crookes tube works


Diagram showing a Crookes tube circuit.

Crookes tubes are cold cathode 
<http://en.wikipedia.org/wiki/Cold_cathode> tubes, meaning that they do 
not have a heated filament 
<http://en.wikipedia.org/wiki/Electrical_filament> in them that releases 
electrons <http://en.wikipedia.org/wiki/Electron> as the later 
electronic vacuum tubes <http://en.wikipedia.org/wiki/Vacuum_tube> 
usually do. Instead, electrons are generated by the ionization 
<http://en.wikipedia.org/wiki/Ionization> of the residual air by a high 
DC <http://en.wikipedia.org/wiki/Direct_current> voltage 
<http://en.wikipedia.org/wiki/Voltage> (from a few kilovolts 
<http://en.wikipedia.org/wiki/Kilovolts> to about 100 kilovolts) applied 
between the electrodes, usually by an induction coil 
<http://en.wikipedia.org/wiki/Induction_coil> (a "Ruhmkorff coil"). The 
Crookes tubes require a small amount of air in them to function, from 
about 10^-6 to 5×10^-8 atmosphere 
<http://en.wikipedia.org/wiki/Atm_%28unit%29> (7×10^-4 - 4×10^-5 torr 
<http://en.wikipedia.org/wiki/Torr_%28unit%29> or 0.1-0.005 pascal 
<http://en.wikipedia.org/wiki/Pascal_%28unit%29>).
When high voltage <http://en.wikipedia.org/wiki/Voltage> is applied to 
the tube, the electric field 
<http://en.wikipedia.org/wiki/Electric_field> accelerates the small 
number of electrically charged ions <http://en.wikipedia.org/wiki/Ion> 
always present in the gas, created by natural processes like 
photoionization <http://en.wikipedia.org/wiki/Photoionization> and 
radioactivity <http://en.wikipedia.org/wiki/Radioactivity>. These 
collide with other gas molecules 
<http://en.wikipedia.org/wiki/Molecule>, knocking electrons off them and 
creating more positive ions in a chain reaction called a Townsend 
discharge <http://en.wikipedia.org/wiki/Townsend_discharge>. All the 
positive ions are attracted to the cathode 
<http://en.wikipedia.org/wiki/Cathode> or negative electrode. When they 
strike it, they knock large numbers of electrons out of the surface of 
the metal, which in turn are repelled by the cathode and attracted to 
the anode <http://en.wikipedia.org/wiki/Anode> or positive electrode. 
These are the cathode rays <http://en.wikipedia.org/wiki/Cathode_ray>.
Enough of the air has been removed from the tube that most of the 
electrons can travel the length of the tube without striking a gas 
molecule. The high voltage accelerates these low-mass particles to a 
high velocity (about 37,000 miles per second, or 59,000 km/s, about 20 
percent of the speed of light 
<http://en.wikipedia.org/wiki/Speed_of_light>, for a typical tube 
voltage of 10 kV^[5] 
<http://en.wikipedia.org/wiki/Crookes_tube#cite_note-5> ). When they get 
to the anode end of the tube, they have so much momentum 
<http://en.wikipedia.org/wiki/Momentum> that, although they are 
attracted to the anode, many fly past it and strike the end wall of the 
tube. When they strike atoms in the glass, they knock their orbital 
electrons <http://en.wikipedia.org/wiki/Atomic_orbital> into a higher 
energy level <http://en.wikipedia.org/wiki/Energy_level>. When the 
electrons fall back to their original energy level, they emit light. 
This process, called fluorescence 
<http://en.wikipedia.org/wiki/Fluorescence>, causes the glass to glow, 
usually yellow-green. The electrons themselves are invisible, but the 
glow reveals where the beam of electrons strikes the glass. Later on, 
researchers painted the inside back wall of the tube with a phosphor 
<http://en.wikipedia.org/wiki/Phosphor>, a fluorescent chemical such as 
zinc sulfide <http://en.wikipedia.org/wiki/Zinc_sulfide>, in order to 
make the glow more visible. After striking the wall, the electrons 
eventually make their way to the anode, flow through the anode wire, the 
power supply, and back to the cathode.

The different glowing regions possible in a Crookes tube.

The above only describes the motion of the electrons. The full details 
of the action in a Crookes tube are complicated, because it contains a 
nonequilibrium plasma 
<http://en.wikipedia.org/wiki/Plasma_%28physics%29> of positively 
charged ions <http://en.wikipedia.org/wiki/Ion>, electrons 
<http://en.wikipedia.org/wiki/Electron>, and neutral atoms 
<http://en.wikipedia.org/wiki/Atom> which are constantly interacting. At 
higher gas pressures, above 10^-6 atm (0.1 Pa), this creates different 
colored glowing regions in the gas, depending on the pressure in the 
tube (see diagram). The details were not fully understood until the 
development of plasma physics 
<http://en.wikipedia.org/wiki/Plasma_physics> in the early 20th century.

   The discovery of X-rays


When the voltage applied to a Crookes tube is high enough, around 5,000 
volts <http://en.wikipedia.org/wiki/Volt> or greater,^[9] 
<http://en.wikipedia.org/wiki/Crookes_tube#cite_note-9> it can 
accelerate the electrons to a fast enough velocity to create X-rays 
<http://en.wikipedia.org/wiki/X-rays> when they hit the anode or the 
glass wall of the tube. The fast electrons emit X-rays when their path 
is bent sharply as they pass near the high electric charge of an atom's 
nucleus <http://en.wikipedia.org/wiki/Atomic_nucleus>, a process called 
bremsstrahlung <http://en.wikipedia.org/wiki/Bremsstrahlung>, or they 
knock an atom's inner electrons into a higher energy level 
<http://en.wikipedia.org/wiki/Energy_level>, and these in turn emit 
X-rays as they return to their former energy level, a process called 
X-ray fluorescence <http://en.wikipedia.org/wiki/X-ray_fluorescence>. 
Many early Crookes tubes undoubtedly generated X-rays, because early 
researchers such as Ivan Pulyui 
<http://en.wikipedia.org/wiki/Ivan_Pulyui> had noticed that they could 
make foggy marks on nearby unexposed photographic plates 
<http://en.wikipedia.org/wiki/Photographic_plate>. On November 8, 1895, 
Wilhelm Röntgen <http://en.wikipedia.org/wiki/Wilhelm_R%C3%B6ntgen> was 
operating a Crookes tube covered with black cardboard when he noticed 
that a nearby fluorescent screen glowed faintly.^[10] 
<http://en.wikipedia.org/wiki/Crookes_tube#cite_note-10> He realized 
that some unknown invisible rays from the tube were able to pass through 
the cardboard and make the screen fluoresce. He found that they could 
pass through books and papers on his desk. Röntgen began to investigate 
the rays full-time, and on December 28, 1895, published the first 
scientific research paper on X-rays.^[11] 
<http://en.wikipedia.org/wiki/Crookes_tube#cite_note-11> Röntgen was 
awarded the first Nobel Prize in Physics 
<http://en.wikipedia.org/wiki/Nobel_Prize_in_Physics> (in 1901) for his 
discoveries.
The medical applications of X-rays created the first practical use for 
Crookes tubes, and workshops began manufacturing specialized Crookes 
tubes to generate X-rays, the first X-ray tubes. The anode was made of a 
heavy metal, usually platinum <http://en.wikipedia.org/wiki/Platinum>, 
which generated more X-rays, and was tilted at an angle to the cathode, 
so the X-rays would radiate through the side of the tube. The cathode 
had a concave spherical surface which focused the electrons into a small 
spot around 1 mm in diameter on the anode, in order to approximate a 
point source of X-rays, which gave the sharpest radiographs 
<http://en.wikipedia.org/wiki/Radiograph>. These cold cathode type X-ray 
tubes were used until about 1920, when they were superseded by the hot 
cathode <http://en.wikipedia.org/wiki/Hot_cathode> Coolidge X-ray tube.










--
Alton Smith antiqueradiotubes.com http://www.flickr.com/photos/91001059@N08/
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